According to me xperia xz premium is the best because it comes with latest security patch, android version ,its looks are great too and comes with gorilla glass 5, and 801ppi display, so its display is best among all others

Sony Xperia XZ Premium is better than Samsung Galaxy S8 as it has Around 94% more pixels than Samsung Galaxy S8. More resolution means sharper and crisper screen, Around 58% more mega pixels (MP) than Samsung Galaxy S8. More resolution generally means better picture quality, though it's not always necessary, Around 7% more Battery Capacity than Samsung Galaxy S8. With more battery size, device's battery can generally last more time, though it depends on various other factors too.